An observational based analysis of ozone trends and production for urban areas in North Carolina

An observational based analysis of ozone production for Raleigh and Charlotte, North Carolina, was performed for the years 1981–1990. A trend analysis was carried out for the 10 yr period for Raleigh. The third quartile average for Raleigh indicated a slight upward trend of about 0.5 parts per billion by volume (ppbv) per year in ozone concentration, but this may not be statistically significant. During the period studied, Raleigh was designated as out of compliance for ozone, with a classification of moderate for non-attainment areas in 1989. There were three exceedences of the National Ambient Air Quality Standard (NAAQS) of 0.12 parts per million by volume (ppmv) each in 1980, 1983, and 1987; and 13 exceedences in 1988. Based on a regression analysis, it was identified that the variability in ozone concentration in the Raleigh area is best correlated with maximum temperature and solar radiation, and also weakly correlated with daily average wind speed and wind direction. But, the local meteorological parameters could only explain 35–53% of the total variance. A delta ozone analysis was performed to obtain an estimate of the contribution to the production of ozone made by the metropolitan areas of Raleigh and Charlotte, North Carolina. During the summer of 1989, the city of Raleigh provided an average of about 25 ppbv of additional ozone to air advecting over the city. The amount of ozone produced by the metropolitan area of Charlotte for 1984–1991 averaged about 10–15 ppbv with a slight upward trend in ozone production (1.34±0.78 ppbv per year). These values are compared to a published value of 30–40 ppbv of ozone for Atlanta, Georgia, during 1979–1987.